This invention relates generally to flame-retardant materials and insulating materials and, more particularly, to fiber-free moldings containing binders and selected fillers.
Products containing mineral, ceramic and glass fibers are widely used in the field of heat and sound insulation. Large quantities of such materials—mostly in sheet or shell form—are also used for the preventive fire protection of buildings.
One of the advantages of these materials is their favorable thermal insulation capacity coupled with high mechanical strength. The materials in question are also distinguished by their easy machinability, low weight, high heat resistance and favorable self-burning behavior. Many of these “insulation materials” are classified as noninflammable building materials (Class A Building Materials according to DIN 4102, Part 1) or at least as flame-resistant building materials (Class B1 Building Materials according to DIN 4102, Part 1).
Mineral, ceramic and glass fibers are also known collectively as MMMF fibers. MMMF is the abbreviation for man-made mineral fibers. The toxicological effect of MMMF fibers is a contentious issue (see F. W. Löffler: Aktuelle Aspekte zur Problematik der künstlichen Mineralfasern, Keramik und Glas 2, 14 (1996)). Depending on their length-to-diameter ratio and their chemical composition, many of these fibers are classified as carcinogenic materials under the law on hazardous materials (see Technische Regeln für Gefahrstoffe TRGS 905 and TRGS 906). The absence of fibers is extremely important for factory hygiene and toxicological reasons because fibers are released both during processing of the moldings and also—through mechanical stressing—during their use (VDI Kolloquium “Faserförmige Stäube”, 9/93).
Accordingly, there is an interest in MMMF-free products which have a similar property spectrum to the fiber-based materials mentioned above. Known MMMF-free materials are, for example, vermiculite, cellular concrete, perlite, calcium silicate and gypsum products. Thus, a highly filled phenolic resin foam is described, for example, in DE-A1 3644468 (Isobloc Hüls). In this case, aluminium hydroxide and silicon oxide are used as fillers in quantities of more than 100% by weight, based on the phenolic resin. The result of this is that the rigid foams formed are correspondingly heavy (density 350 kg/m3). Another possibility is to use phenolic resins in combination with furane resins, as described in European patent application EP-A2 0 325 935 (Rühl) and in DE-C14227536 (Rühl), DE-C1 3407512 (Rühl) and DE-B1 2825295. The products described therein use as fillers the main component aluminium hydroxide and added quantities of boric acid, sodium tetraborate and cryolite which are said to retard the burning rate of the organic foam matrix. The disadvantage of these products lies inter alia in the considerable outlay involved in avoiding odor emissions during production and in adjustment of the reactivity of the resin. None of the hitherto known materials represents an ideal replacement for the fiber-containing building materials because the properties of fiber-containing products cannot all be achieved.
Accordingly, the problem addressed by the present invention was to produce fiber-free moldings which would be comparable in their property spectrum with fiber-containing materials. In particular, the replacement materials would be comparable with the fiber-containing materials in their weight, their easy processability and their simple thermoformability under pressure. In addition, the materials according to the invention would show favorable self-burning behavior so that they could be used in the preventive fire protection of buildings. Economic production would of course also be desirable.